Today at the end of the office the Vs. Benedicámus Dómino. is sung with double Allelúia. as on Easter Sunday, 783; and thereafter the Allelúia. is not said all the way up to the Easter Vigil.

From page 783, here is the versicle :

(If you are not familiar with it, in the calendar for the traditional Latin Mass, there is a pre-Lent season which begins three Sundays before Ash Wednesday. These are called Septuagesima, Sexagesima, and Quinquagesima, the names being derived from the numbers 70, 60 and 50. These numbers are not exact but rather symbolic; they represent the count-down of days until Easter. Thus the season of Lent is also called Quadragesima, for its 40 days.)